Multilayer constructs for metabolite strips providing inert surface and mechanical advantage

ABSTRACT

The present disclosure relates to multilayer constructs for producing metabolite strips. The multilayer constructs include a substrate layer having a top surface and a bottom surface, a thin film metal conductor layer formed on the top surface of the substrate layer and configured to act as an electrode, and a Transparent Conductive Oxide (TCO) protective layer deposited on top of the metal conductor layer. The metabolic strips can be used, along with various measuring devices, for determining the presence of certain analytes in a specimen and for various like applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/074,628, filed Mar. 18, 2016, now U.S. Pat. No. 10,197,522, whichclaims priority to U.S. Provisional Patent Application Ser. No.62/208,290, filed on Aug. 21, 2015; U.S. Provisional Patent ApplicationSer. No. 62/134,806, filed on Mar. 18, 2015; and U.S. Provisional PatentApplication Ser. No. 62/134,795, filed on Mar. 18, 2015; the disclosuresof which are hereby fully incorporated by reference.

BACKGROUND

The present disclosure relates to materials for multilayer constructsuseful for producing metabolite test strips. In particular, anon-conductive substrate layer, a metal conductor layer, and an oxidizedTransparent Conducting Oxide (TCO) layer are provided to impart superiorelectrochemical response while maintaining desired mechanicalproperties, and will be described with particular reference thereto.However, it is to be appreciated that the present disclosure is alsoamenable to other like applications.

Metabolite test strips can be used in several applications, such asvarious metering devices for testing and/or determining certaincharacteristics and/or the presence of analytes in a specimen. Forexample, the test strips can be used as biosensors for measuring theamount of an analyte (e.g., glucose) in a biological fluid (e.g.,blood). These biosensors use a redox enzyme (e.g., glutathioneperoxidases (GPX), nitric oxide synthase (eNOS, iNOS, and nNOS),peroxiredoxins, super oxide dismutases (SOD), thioredoxins (Trx), andthe like), as the biological component responsible for the selectiverecognition of the analyte of interest (e.g., glucose).

The biological fluid sample is introduced into the reaction chamber ofthe test strip and the test strip is connected to a measuring devicesuch as a meter for analysis using the test strip's electrodes. Theanalyte in the sample undergoes a reduction/oxidation reaction at theworking electrode (where the redox enzyme is located) while themeasuring device applies a biasing potential signal through theelectrodes of the test strip. The redox reaction produces an outputsignal in response to the biasing potential signal. The output signalusually is an electronic signal, such as potential or current, which ismeasured and correlated with the concentration of the analyte in thebiological fluid sample.

Metabolite test strips of this type are made from multilayer constructs.An important feature of these multilayer constructs is that theirmaterials have a reduced sensitivity to heat, humidity and degradation,while maintaining mechanical robustness and good electricalconductivity. Moreover, it would be advantageous to provide suchmaterials at a reduced cost for expanding markets where utilization ofthese materials is rapidly expanding.

It would be desirable to develop new materials from which multilayerconstructs can be built. These materials are desirably less affected byenvironmental factors such as air and water, and are mechanically robustwhile maintaining electrochemical preferentiality. In addition,conductive layers in such test strips are typically made from expensiveprecious metals, such as silver, gold, palladium, or platinum. It wouldbe desirable to develop new alloys that can be used in multilayerconstructs that have superior electrochemical response and distinctmechanical advantages. It would also be desirable if such alloys did notinclude precious metals, which are costly.

BRIEF DESCRIPTION

The present disclosure relates multilayer constructs having a substratelayer, a metal alloy conductor layer which is configured to act as oneor more electrodes, and an oxidized, preferably fully oxidized, TCOprotective layer. The TCO protective layer advantageously impartselectrochemical preferentiality and mechanical stability over a singlelayer construction compared to pure metal conductors or metal alloyswhich are presently used in the industry.

Along these lines, disclosed in various embodiments are multilayerconstructs having a substrate layer having a top surface and a bottomsurface, a thin film metal conductor layer formed on the top surface ofthe substrate layer, and a protective layer deposited on top of the thinfilm metal conductor layer.

In some embodiments, the thin film metal conductor layer and the TCOprotective layer are processed to include patterning on their surfaces.In other embodiments, the conductor layer and the TCO protective layerhave substantially continuous surfaces.

Also disclosed herein are alloys for use as a conductor layer in amultilayer construct. In some embodiments, the alloy can have aresistivity of less than 100 ohms/sq at a preferred thickness of about10 nanometers to about 100 nanometers. In particular embodiments, thealloys are nickel-based alloys. The nickel-based alloy may furtherinclude aluminum, chromium, molybdenum, niobium, titanium, tantalum,vanadium, rhenium, ruthenium, hafnium, tungsten, cobalt, boron, yttrium,platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and/or osmium(Os). A cobalt-based alloy is also contemplated. In other particularembodiments, the metal alloy is an indium or tin based alloy.

This type of construction is less susceptible to both electrochemicaland mechanical degradation and offers a lower cost solution having amechanical and electrochemical advantage.

The present disclosure also relates to multilayer constructs having anon-conductive substrate layer, a thin film metal alloy conductor layer,and a fully oxidized TCO protective layer. The TCO protective layeradvantageously imparts electrochemical preferentiality and mechanicalstability over a single layer construction compared to pure metalconductors without a protective TCO layer is presently used in theindustry.

Also disclosed in various embodiments are multilayer constructs having anon-conductive substrate layer having a top surface and a bottomsurface, a thin film metal alloy conductor layer formed on the topsurface of the substrate layer, and a fully oxidized TCO protectivelayer deposited on top of the conductor layer. The bottom surface of thesubstrate layer is free of additional conductive layers.

In a further embodiment, the conductor layer and the TCO protectivelayer are processed to include patterning on their surfaces. In otherembodiments, the conductor layer and the TCO protective layer havesubstantially continuous surfaces.

These and other non-limiting characteristics of the disclosure are moreparticularly disclosed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

The FIGURE is a cross-sectional view of an exemplary multilayerconstruct of the present disclosure.

DETAILED DESCRIPTION

A more complete understanding of the components, processes andapparatuses disclosed herein can be obtained by reference to theaccompanying drawings. These figures are merely a schematicrepresentations based on convenience and the ease of demonstrating thepresent disclosure, and are, therefore, not intended to indicaterelative size and dimensions of the devices or components thereof and/orto define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

Numerical values in the specification and claims of this applicationshould be understood to include numerical values which are the same whenreduced to the same number of significant figures and numerical valueswhich differ from the stated value by less than the experimental errorof conventional measurement technique of the type described in thepresent application to determine the value.

All ranges disclosed herein are inclusive of the recited endpoint andindependently combinable (for example, the range of “from 2 grams to 10grams” is inclusive of the endpoints, 2 grams and 10 grams, and all theintermediate values).

The term “about” can be used to include any numerical value that cancarry without changing the basic function of that value. When used witha range, “about” also discloses the range defined by the absolute valuesof the two endpoints, e.g., “about 2 to about 4” also discloses therange “from 2 to 4.” The term “about” may refer to plus or minus 10% ofthe indicated number.

A metabolic test strip is typically formed from: (1) a substrate; (2) apair of electrodes; and (3) a reagent layer that reacts with theanalyte, and generally contains the redox enzyme and electron mediators.

The FIGURE is a cross-sectional view of a multilayer construct 10 fromwhich an electrochemical test strip can be made. The multilayerconstruct 10 has a substrate layer 20, a metal conductor layer 30, and aprotective transparent conducting oxide (TCO) layer 40. The substratelayer has a top surface 22 and a bottom surface 24. The conductor layer30, and TCO protective layer 40 are coated or deposited onto the topsurface 22 of the substrate 20, while the bottom surface 24 of thesubstrate remains free of additional layers.

The substrate 20 is generally made of a non-conductive material,preferably a polymer web. Such materials include plastics, for examplepolyvinyl chloride, polycarbonate, polysulfone, nylon, polyurethane,cellulose nitrate, cellulose propionate, cellulose acetate, celluloseacetate butyrate, polyester, polyimide, polypropylene, polyethylene andpolystyrene.

Conductive layers are typically made from pure metals which are soft andbrittle, having a low resistance to deformation but having highelectrical conductivity. Moreover, precious pure metals are often used,which are costly. To increase the structural rigidity and reduce thecost of the conductor layer, a custom metal alloy can be used for theconductive layer instead of a pure metal. The custom metal alloydesirably increases the conductive layer's resistance to deformation anddecreases cost, while desired electrical conductivity properties can bemaintained.

The metal alloy itself can be a binary, tertiary, or quaternary alloy ofsuitable metals. In particular embodiments, the alloy contains nickel incombination with elements such as aluminum, chromium, molybdenum,niobium, titanium, tantalum, vanadium, rhenium, ruthenium, hafnium,tungsten, cobalt, boron, yttrium, platinum (Pt), palladium (Pd), rhodium(Rh), iridium (Ir), and/or osmium (Os). The alloy may contain about 10atomic percent (at %) to about 75 at % of nickel, and about 25 at % toabout 90 at % of other elements. Any combination of one or more of theother elements is contemplated. The alloy may be formed by in-situsputtering. Desirably, one would fabricate a sputtering target from thealloy, as this allows deposition uniformity to be maintained.

In other embodiments, the alloy contains cobalt in combination withelements such as nickel, aluminum, chromium, molybdenum, niobium,titanium, tantalum, vanadium, rhenium, ruthenium, hafnium, tungsten,boron, yttrium, platinum (Pt), palladium (Pd), rhodium (Rh), iridium(Ir), and/or osmium (Os). The alloy may contain about 10 atomic percent(at %) to about 75 at % of cobalt, and about 25 at % to about 90 at % ofother elements. Any combination of one or more of the other elements iscontemplated. The alloy may be formed by in-situ sputtering. Desirably,one would fabricate a sputtering target from the alloy, as this allowsdeposition uniformity to be maintained.

In particular embodiments, the elemental additions in the nickel-basedsuper-alloy are gamma prime (y′) formers such as aluminum, titanium,niobium, tantalum, and hafnium. Desirable properties from gamma primenickel-based super-alloys can include long-time stability and addedductility imparting strength without lowering fracture toughness.

In other embodiments, the elemental additions in the nickel-basedsuper-alloy include carbon combined with carbide formers such aschromium, molybdenum, tungsten, niobium, tantalum, and titanium.Desirable properties from carbide strengthened nickel-based super-alloyscan include the formation of grain boundaries which increase rupturestrength at high temperature.

In further particular embodiments, the elemental additions in thecobalt-based super-alloy include carbon combined with carbide formerssuch as chromium, molybdenum, tungsten, niobium, tantalum, and titanium.Desirable properties from cobalt-based super-alloys hardened by carbideprecipitation include hot corrosion resistance, oxidation resistance,and thermal fatigue resistance and weldability.

Alternatively, the metal alloy may be an indium alloy that containsindium in combination with elements such as oxygen, tin, nickel, cobalt,aluminum, chromium, molybdenum, niobium, titanium, tantalum, vanadium,rhenium, ruthenium, hafnium, tungsten, boron, yttrium, platinum (Pt),palladium (Pd), rhodium (Rh), iridium (Ir), and/or osmium (Os). Thealloy may contain about 10 atomic percent (at %) to about 75 at % ofindium, and about 25 at % to about 90 at % of other elements. Anycombination of one or more of the other elements is contemplated, thoughoxides are particularly contemplated.

The metal alloy may also be a tin alloy that contains indium incombination with elements such as oxygen, indium, nickel, cobalt,aluminum, chromium, molybdenum, niobium, titanium, tantalum, vanadium,rhenium, ruthenium, hafnium, tungsten, boron, yttrium, platinum (Pt),palladium (Pd), rhodium (Rh), iridium (Ir), and/or osmium (Os). Thealloy may contain about 10 atomic percent (at %) to about 75 at % oftin, and about 25 at % to about 90 at % of other elements. Anycombination of one or more of the other elements is contemplated, thoughoxides are particularly contemplated.

These metals can be used to provide physical and electrical propertyadvantages when used with specific systems, such as metabolic teststrips. In such systems, the metal alloy conductive layer 30 can beprocessed to include at least one pattern formed from the alloyconductive layer. The pattern can be an electrode formed from the alloyconductive layer 30 by shadow masking, laser ablating, or lithography.The metal alloy conductive layer 30 can also be provided without anypattern formed thereon. That, the metal alloy conductive layer 30 can beprovided with substantially continuous surfaces.

The metal alloy, such as a nickel-containing alloy, desirably exhibitimproved physical and electrical properties. One improved property isthe thickness of the metal alloy conductor layer, which can be verythin. In embodiments, the metal alloy conductor layer can have athickness of about 10 nanometers to about 100 nanometers. Anotherimproved property is the electrical conductivity of the conductor layer,which can be less than 100 ohms/square (Q/sq) at the desired thickness.The metal alloy may also allow for improved stability, as measured byelectrochemical response stability over time when exposed to humidityand temperature variations, or as measured by changes in adhesion and/orabrasion differences when exposed to a reagent. Other desirableproperties can include physical contact durability, lowered contactresistance for lowered/more consistent bias response, and/or bettercohesion for finer line formation in circuitry.

Physical and electrical properties which the metal alloy conductor layerprovides may include thinness of the electrode, better electricalconductivity, stability over time, physical contact durability, loweredcontact resistance for lowered/more consistent bias response, and/orbetter cohesion for finer line formation in circuitry.

The metal conductor layer 30 may also be a pure metal. The pure metalconductor layer 30 can be formed on the substrate 20 by any method knownin the art, such as by sputtering. The pure metal conductor layer 30 canbe any suitable pure metallic conductor. Examples of pure metals includealuminum, antimony, barium, beryllium, bismuth, boron, cadmium, cerium,chromium, cobalt, copper, erbium, gadolinium, gallium, germanium, gold,hafnium, indium, iridium, iron, lanthanum, lead, magnesium, manganese,molybdenum, neodymium, nickel, niobium, osmium, palladium, platinum,praseodymium, rhenium, rhodium, ruthenium, samarium, selenium, silicon,silver, tantalum, tellurium, terbium, tin, titanium, tungsten, vanadium,ytterbium, yttrium, zinc, and zirconium. Preferably, the pure metalconductor includes aluminum, cobalt, copper, gallium, gold, indium,iridium, iron, lead, magnesium, nickel, niobium, osmium, palladium,platinum, rhenium, rhodium, selenium, silicon, silver, tantalum, tin,titanium, tungsten, uranium, vanadium, zinc, zirconium and mixturesthereof. Most preferably, the pure metal conductor includes gold,platinum, palladium, ruthenium, and iridium.

Generally, a pure metal is defined as one composed entirely of a singleelement. Those skilled in the art, however, will recognize that due tothe difficulty in removing all traces of other elements or contaminants,a pure metal may also refer to one containing only unavoidablecontaminants, impurities, etc.

These metals can be used to provide physical and electrical propertyadvantages when used with specific systems, such as electrochemical teststrips. In such systems, the pure metal conductive layer 30 can beprocessed to include at least one pattern formed from the conductivelayer. The pattern can be an electrode formed on the pure metalconductor layer 30 by scribing, scoring, shadow masking, laser ablating,or lithography. Scribing or scoring may be done by mechanically scribingthe pure metal conductor layer. The pure metal conductive layer 30 canalso be provided without any pattern formed thereon. That is, the puremetal conductive layer 30 can be provided with substantially continuoussurfaces.

Physical and electrical properties which the pure metal conductor layerprovides may include thinness of the electrode, better electricalconductivity, stability over time, physical contact durability, loweredcontact resistance for lowered/more consistent bias response, and/orbetter cohesion for finer line formation in circuitry.

To further increase the structural rigidity of the metal alloy conductorlayer 30, a TCO protective layer 40 can be formed on top of the metalconductor layer. By capping the metal conductor layer 30, the TCO layer40 adds mechanical robustness to the multilayer construct by increasingresistance to deformation of the metal conductor layer 30. A mechanicaladvantage from abrasion is also achieved with the protective TCO layer40. The TCO protective layer is also highly electrically conductive,thus the conductivity of the overall multilayer construct is notaffected. In addition, the multilayer construct may eventually include achemical reagent layer. Thus, the TCO layer acts as a protective cap orlayer which provides chemical stability.

The TCO layer 40 can be coated onto the metal conductor layer 30 by anymethod known in the art, including planar magnetron sputtering, closedfield magnetron sputtering, ion beam sputtering, rotatable magnetronsputtering, reactive thermal and electron beam evaporation, and CVD andPECVD processes. The protective TCO layer 40 can also be processed toinclude at least one pattern formed from the TCO layer. The pattern canbe an electrode formed from the protective TCO layer 40 by shadowmasking, laser ablating, or lithography. The at least one pattern formedfrom the TCO layer is substantially similar to that of the at least onepattern formed from the metal conductor layer 30. The TCO layer 40 canalso be provided without any pattern formed thereon such that the TCOlayer has substantially continuous surfaces.

TCO's have high optical transmission at visible wavelengths andelectrical conductivity close to that of metals. An important feature ofthe TCO is that it is transparent while remaining electricallyconductive. TCO's are generally n-type large band gap semiconductorswith a relatively high concentration of free electrons in the conductionband, however, p-type materials are also contemplated. The wide bandgapprovides for relatively high optical transmittance and free electronsincrease electrical conductivity. To increase their conductivity, TCO'scan be doped with donors (n-type) and acceptors (p-type). The TCO layeritself can be a binary, ternary, or quaternary compound. Examplesinclude the most commonly used and widely developed TCO, indium tinoxide (ITO), which is Sn-doped indium oxide (In₂O₃). Other TCO examplesinclude zinc oxide (ZnO), tin dioxide (SnO₂), cadmium oxide (CdO),tantalum oxide (Ta₂O), gallium indium oxide (GaInO₃), cadmium antimonyoxide (CdSb₂O₃), titanium dioxide (TiO₂), tungsten trioxide (WO₃),molybdenum trioxide (MoO₃), and the like.

Generally, the TCO layer 40 comprises a large band gap semiconductor. Toincrease their conductivity, TCO's can be doped with donors (n-type) andacceptors (p-type). In one embodiment, the TCO layer 40 is indium tinoxide (ITO), which is an indium oxide (In₂O₃) semiconductor doped withSn. Other embodiments of the present disclosure contemplate the use ofother TCO's. In one embodiment, a zinc oxide (ZnO) semiconductor isdoped with a suitable donor such as Al, Ga, B, In, Y, Sc, F, V, Si, Ge,Ti, Zr, Hf, Mg, As, H, and combinations thereof. In yet anotherembodiment, a tin dioxide (SnO₂) semiconductor is doped with a suitabledonor such as Sb, F, As, Nb, Ta, and combinations thereof. In yetanother embodiment, a cadmium oxide (CdO) semiconductor is doped with asuitable donor such as In or Sn. In yet another embodiment, a tantalumoxide (Ta₂O) semiconductor forms the TCO layer. In year anotherembodiment, a gallium indium oxide (GaInO₃) semiconductor is doped witha suitable donor such as Sn or Ge. In yet another embodiment, a CdSb₂O₃semiconductor is used as the TCO layer. In yet another embodiment, atitanium dioxide (TiO₂) semiconductor is doped with a suitable donorsuch as Ti²⁺ or Ti³⁺. In yet another embodiment, a tungsten trioxide(WO₃) semiconductor is doped with a suitable donor such as W³⁺, W⁴⁺, orW⁵⁺. In yet another embodiment, a molybdenum trioxide (MoO₃)semiconductor is doped with a suitable donor such as Mo³⁺, Mo⁴⁺, orMo⁵⁺.

These TCO's can be used to provide specific physical and electricalproperty advantages to the multilayer constructs disclosed herein, suchas electrical conductivity and optical transparency, high physicaldensity, low specific electrical resistance, high environmental andtemperature stability, mechanical durability and solubility. The TCOprotective layer 40 can provide these properties without addingthickness in specific systems, such as electrochemical test strips. Inembodiments, the TCO protective layer can have a thickness of about 100nanometers. Preferably, the TCO protective layer has a thickness ofabout 20 nanometers to about 50 nanometers.

The resulting multilayer construct formed from the substrate, conductivemetal alloy layer, and TCO protective layer desirably exhibit improvedphysical and electrical properties. One improved property is mechanicalrobustness of the multilayer construct while improving or maintaining anadequate electrical conductivity across the electrodes. The multilayerconstruct may also exhibit improved stability, as measured byelectrochemical response stability over time when exposed to humidityand temperature variations, or as measured by changes in adhesion and/orabrasion differences when exposed to the reagent. Other desirableproperties can include physical contact durability, lowered contactresistance for lowered/more consistent bias response, ease oftransportation and handling, reduced cost, and/or better cohesion forfiner line formation in circuitry.

The following examples are provided to illustrate the constructs,methods, systems, articles, and properties of the present disclosure.The examples are merely illustrative and are not intended to limit thedisclosure to the materials, conditions, or process parameters set forththerein.

Example 1

A conductive layer was formed by sputtering gold onto a surface of asubstrate. A protective TCO layer was formed on top of the conductivelayer by sputtering ITO on the gold conductive layer. Table 1 belowlists the target thicknesses for the gold conductive layer and the ITOlayer, along with the resultant resistivities observed. The resistancesrepresent the average measured surface resistance across five testpoints.

TABLE 1 Target thicknesses and resultant surface resistances of Gold/ITOmultilayer construct. Target Thickness - Gold Target Thickness - ITOSurface Resistance Angstroms (Å) Angstroms (Å) Ohms/sq. (Ω/sq.) 200 *4.33 250 600 2.98 250 300 3.26 75 600 13.26 75 300 14.35

Example 2

A conductive layer was formed by sputtering palladium onto a surface ofa substrate. A protective TCO layer was formed on top of the conductivelayer by sputtering ITO on the palladium conductive layer. Table 2 belowlists the target thicknesses for the palladium conductive layer and theITO layer, along with the resultant resistivities observed. Theresistances represent the average measured surface resistance acrossfive test points.

TABLE 2 Target thicknesses and resultant surface resistances ofPalladium/ITO multilayer construct. Target Thickness - Palladium TargetThickness - ITO Surface Resistance Angstroms (Å) Angstroms (Å) Ohms/sq.(Ω/sq.) 150 300 23.4 400 300 5.91 400 600 5.4 150 600 19.0

Example 3

A conductive layer was formed by sputtering titanium onto a surface of asubstrate. A protective TCO layer was formed on top of the conductivelayer by sputtering indium zinc oxide (IZO) on the titanium conductivelayer. Table 2 below lists the target thicknesses for the palladiumconductive layer and the ITO layer, along with the resultantresistivities observed.

TABLE 3 Target thicknesses and resultant surface resistances ofTitanium/IZO multilayer construct. Target Thickness - Titanium TargetThickness - IZO Surface Resistance Angstroms (Å) Angstroms (Å) Ohms/sq.(Ω/sq.) 200 300 52.5 200 200 60 300 100 42 400 100 30

The present disclosure has been described with reference to theexemplary embodiments. Obviously, modifications and alterations willoccur to others upon reading and understanding the preceding detaileddescription. It is intended that the present disclosure be construed asincluding all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

1. A multilayer construct comprising: a substrate layer having a topsurface and a bottom surface; a thin film metal conductor layer formedon the top surface of the substrate layer, wherein the conductor layeris formed from a metal alloy that is a nickel-based alloy, acobalt-based alloy, an indium-based alloy or a tin-based alloy; and aprotective layer deposited on a top surface of the conductor layer,wherein the protective layer is formed from an oxidized TransparentConducting Oxide (TCO).
 2. The multilayer construct of claim 1, furthercomprising a reagent layer.
 3. The multilayer construct of claim 1,wherein the bottom surface of the substrate layer is free of additionalconductive layers.
 4. The multilayer construct of claim 1, wherein thesubstrate layer is a non-conductive polymer web.
 5. The multilayerconstruct of claim 4, wherein the non-conductive polymer web is selectedfrom the group consisting of polyvinyl chloride, polycarbonate,polysulfone, nylon, polyurethane, cellulose nitrate, cellulosepropionate, cellulose acetate, cellulose acetate butyrate, polyester,polyimide, polypropylene, polyethylene, polystyrene, and combinationsthereof.
 6. The multilayer construct of claim 1, wherein the metal alloyfurther includes aluminum, niobium, titanium, tantalum, rhenium,hafnium, boron, yttrium, chromium, molybdenum, cobalt, ruthenium,tungsten, vanadium, platinum (Pt), palladium (Pd), rhodium (Rh), iridium(Ir), or osmium (Os).
 7. The multilayer construct of claim 1, whereinthe metal alloy has a resistivity of less than 100 ohms/sq at athickness of about 10 nanometers to about 100 nanometers.
 8. Themultilayer construct of claim 1, wherein the conductor layer and theprotective layer are continuous layers.
 9. The multilayer construct ofclaim 1, further comprising a pattern formed from each of the conductorlayer and the protective layer.
 10. The multilayer construct of claim 9,wherein the pattern formed from the conductor layer is the same as thepattern formed from the protective layer.
 11. The multilayer constructof claim 1, wherein the protective layer is a fully oxidized transparentconducting oxide (TCO) layer.
 12. The multilayer construct of claim 11,wherein the protective TCO layer is a semiconductor doped with a donor.13. The multilayer construct of claim 11, wherein the protective TCOlayer is selected from the group consisting of indium tin oxide, zincoxide, tin dioxide, cadmium oxide, tantalum oxide, gallium indium oxide,cadmium antimony oxide, titanium dioxide, tungsten trioxide, molybdenumtrioxide, and combinations thereof.
 14. The multilayer construct ofclaim 1, wherein the protective TCO layer is deposited on the conductorlayer using in-situ sputtering.
 15. A multilayer construct comprising: asubstrate layer having a top surface and a bottom surface; a thin filmmetal conductor layer formed on the top surface of the substrate layer,wherein the conductor layer is a pure metal conductor, and wherein theconductor layer is configured to act as one or more electrodes; and aprotective layer deposited on a top surface of the conductor layer,wherein the protective layer is formed from an oxidized TransparentConducting Oxide (TCO); and an optional reagent layer.
 16. Themultilayer construct of claim 15, wherein the pure metal conductor isselected from the group consisting of aluminum, antimony, arsenic,barium, beryllium, bismuth, boron, cadmium, calcium, cerium, chromium,cobalt, copper, erbium, gadolinium, gallium, germanium, gold, hafnium,indium, iridium, iron, lanthanum, lead, magnesium, manganese,molybdenum, neodymium, nickel, niobium, osmium, palladium, platinum,praseodymium, rhenium, rhodium, ruthenium, samarium, selenium, silicon,silver, tantalum, tellurium, terbium, tin, titanium, tungsten, vanadium,ytterbium, yttrium, zinc, zirconium, and combinations and mixturesthereof.
 17. A system for measuring the presence of an analyte in aspecimen comprising: a metabolic test strip with (1) a substrate layerhaving a top surface and a bottom surface; (2) a thin film metalconductor layer formed on the top surface of the substrate layer,wherein the conductor layer is configured to act as one or moreelectrodes; (3) a Transparent Conductive Oxide (TCO) protective layerdeposited on a top surface of the conductor layer; and (4) a reagentlayer that is capable of reacting with the analyte; and a measuringdevice.
 18. A method of measuring an analyte in a biological fluid,comprising: providing a metabolic test strip with (1) a substrate layerhaving a top surface and a bottom surface; (2) a thin film metalconductor layer deposited on the top surface of the substrate layer,wherein the conductor layer is configured to act as one or moreelectrodes; (3) a Transparent Conductive Oxide (TCO) protective layerdeposited on top of the conductor layer; and (4) a reagent layer that iscapable of reacting with the analyte; coating the metabolic test stripwith a biological fluid so that the analyte reacts with the reagentlayer; and exposing the coated test strip to a measuring device todetermine the presence of a reaction and the analyte in the fluid.